Most forms have the same words across and down. Forms whose
across words are different from the down words are called
“double forms.” When a square, for example, has
different words across and down, it is termed a “double
square.” (Forms that inherently have different words across
and down, such as pyramids,
are not called double.) Double forms are harder to create than
standard forms. See the examples in the diamond and square descriptions; other shapes
shown in this Guide as single can also be constructed as
double.

A hollow form has the same shape as the usual example of that
form, but with a small section missing from the middle. The
missing section is a smaller version of the form’s shape.
Hollow forms have several lines that contain more than one word.
See the example in the diamond description.

For forms that can be created in various orientations, such as
halfsquares and enneagons, “left” and
“right” describe which way the words slant. In left
forms, the words appear to flow from top left to bottom right; in
right forms, they flow from top right to bottom left. See the
word after “left” or “right” in the title
for an example.

Usually seen as squares, progressive forms consist of
successive words that differ by only one letter. The first word
is beheaded and has a new letter added to its end to make the
second word, and so on throughout the form. See the example in
the square description.

Usually seen as squares, all the forms in a sequential set
contain a certain word, which will be seen as the first word in
the first form, the second word in the second form, and so on
until it has appeared in each position once. See the example in
the square description.

In a truncated pyramid or pyramid variation (such as a
pyramidal windmill), the
pyramid’s base is an even number of letters; thus, the
shortest word is two letters long rather than one. See the
example in the pyramid
description.

In most forms, the solver fills in one letter per space. In a
variogram form - most often a square - a space might contain just
one letter, or might contain any number of letters more than
that. Bigram and trigram forms are specific cases of a variogram
form. See the example in the square description.

Variogram forms are often significantly harder than standard
forms. Generally, it is best to clue them as straightforwardly as
possible.

Formists sometimes compose variogram squares to incorporate
some specific idea; for example, to include the sequence NPL in a
number of places, or to have a pattern in the number of letters
used in each space.

In a space where a word crosses itself-such as the first space
in a square-having a long multiletter sequence can be problematic
for solvers. Multiletter sequences should generally be included
in two words.

In a vowelless form, the answers to the clues must have their
vowels removed before they will fit in the shape; similarly for
consonantless forms. In these forms, Y is always considered a
vowel.

Because each answer provides less information to the solver
than usual, it is best to clue the entries as straightforwardly
as possible. The forms editor will sometimes provide extra
information, such as enumerations for any phrases, or NI2/NI3
tags.